So I just chose destroy at the highest EMS I've ever had (about 4100 EMS) not counting Anderson not being shot by the Illusive Man and I have extended cut. At the very end you see N7 dog tags on a pile of rubble then you hear it breath and move. Assuming that's Shepard, how could he have survived just due to more EMS if he's being kept alive by cybernetics and Destroy would have torn all that apart?

The easiest way is if you would finish it with a low EMS ending...... the lower the EMS, the less ships to defend the Cruicible, the more damage it takes on it's way to the Citadel. Your EMS is some kind of failsafe control.

Only a nearly unscathed Crucible can focus the energy output of it's Eezo Core good enough, that almost all if it will be consumed for your red, blue or green decission. The more it's damaged, the more side effects, like explosions, up to massive damage to the whole galaxy will be the result.

Shep 'survives' the High EMS explosion wave because of a more intact Crucible.